JP2002296523A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner with which spot diameters can easily be aligned in a subscanning direction when a plurality of spot diameters in the subscanning direction are not aligned due to the difference in beam widths caused by the variation in the divergence angle of a light source. SOLUTION: In the optical scanner which consists of a combination lens system to collimate luminous flux from a plurality of light sources, a shaping lens system to shape the luminous flux, a light deflection means to deflection- scan the following luminous flux, and a scanning lens system to image the deflection-scanned luminous flux on a medium to be scanned, the plurality of light sources are arrayed in parallel or at a small angle with the main scanning direction, the shaping lens system includes a positive cylindrical lens having power in the main scanning direction at a position nearest to the light source, and a slit to restrict luminous flux width in the subscanning direction is placed at a place separated from the cylindrical lens to the opposite direction of the light source approximately by the focal distance of the cylindrical lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used for a laser printer or the like.

[0002]

2. Description of the Related Art The scanning speed can be doubled by simultaneously scanning two lights. As one conventional example, Patent No. 2741
No. 195 is mentioned. In this case, using a semiconductor laser, 2
A first optical system that linearly images light from two semiconductor laser light sources on the light deflecting means, a light deflecting means that deflects and scans the light from the first optical system, and a deflected light from the light deflecting means Is formed on the medium to be scanned.

[0003]

However, in the case of the above-mentioned prior art, there is a disadvantage that a plurality of spot diameters in the sub-scanning direction are not uniform due to a difference in beam width due to a variation in the spread angle of the light source. Was.

An object of the present invention is to provide an optical scanning device capable of easily adjusting the spot diameter in the sub-scanning direction.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coupling lens system for collimating light beams from a plurality of light sources, a shaping lens system for shaping the light beams, and a light deflecting means for deflecting and scanning the light beams thereafter. In an optical scanning device comprising a scanning lens system for forming an image of a light beam deflected and scanned on a medium to be scanned, a plurality of light sources are arranged parallel or at a small angle to a main scanning direction, and a shaping lens system is closest to the light source. A positive cylindrical lens having power in the main scanning direction is provided at a position, and a slit that restricts the light beam width in the sub-scanning direction is disposed at a position away from the cylindrical lens in a direction opposite to a light source by a focal length of the cylindrical lens substantially. It is achieved by doing.

[0006]

FIG. 1 shows an embodiment of the present invention. Figure 1
For simplicity, only the center light of the light beam is shown.
The first light beam 1A is shown by a solid line, and the second light beam 1B is shown by a dotted line.
FIG. 3 is a view of the main scanning plane viewed from the side. FIG. 4 shows the main scanning plane viewed from above. In FIG. 4, the first light beam 1A is shown by a solid line, and the second light beam 1B is shown by a dotted line.

From the light source 1, two light beams, a first light beam 1A and a second light beam 1B, are generated. Thereafter, each light passes through the collimator lens 2 of the coupling lens system and becomes parallel light. The parallel rays cross between the collimator lens 2 of the coupling lens system and the cylindrical lens 3 of the shaping lens system. After this, cylindrical lens 3 of shaping lens system
And converges only in the main scanning direction. At this time, the light beams are substantially parallel. Then go through slit 4,
Make the light beam width in the sub-scanning direction appropriate. Thereafter, the light passes through the lens 5 of the shaping lens system, the light in the main scanning direction becomes parallel light, and the light in the sub-scanning direction becomes convergent light. After that, the motor
Deflection scan is performed by the light deflection means 7 rotated by 6,
Light passes through a scanning lens system including a lens 8 and a lens 9 and forms an image as a spot 10A and a spot 10B on a medium 10 to be scanned. In the present invention, the slit 4 is provided at a position where the distance from the cylindrical lens 3 of the shaping lens system having the focal length b toward the light deflecting means 7 is only b.

FIG. 2 is an enlarged view of the vicinity of the cylindrical lens of the shaping lens system. The first light beam 3A and the second light beam 3B in FIG. 2 are linear as shown in FIG. 2 at a focal position of a focal distance b, that is, at a distance b behind the cylindrical lens 3 of the shaping lens system. If a slit is formed there, the beam width can be adjusted with high accuracy. In this shaping lens system, the two light beams are separated and independent without overlapping each other only near the position b behind the cylindrical lens of the shaping lens system having the focal length b and near the light deflecting means 7. Since it is difficult to place an adjusting part near the light deflecting means 7, it is preferable to place an adjusting part such as a slit at a position b behind the cylindrical lens of the shaping lens system having the focal length b. The present invention focuses on this point. The slit width is D, the spot diameter on the medium to be scanned is d, the wavelength of the light beam is λ,
Assuming that the focal length of the lens 5 is c, the magnification in the sub-scanning direction of the scanning lens system including the lens 8 and the lens 9 is e, and the pi is π, D and d are generally given by the relationship of the equation (1). d = 4 × λ × c × e / (π × D) (1) The spot diameter on the medium to be scanned can be adjusted by adjusting the slit width D using the relationship of this equation (1). it can. This will be described below with specific numerical values.

The focal length of the collimator lens of the coupling lens system is 7.96 mm, the focal length of the cylindrical lens of the shaping lens system is 29.1 mm, the focal length of the lens of the other shaping lens system is 81.37 mm, and the sub-scanning of the scanning lens system is performed. The directional magnification is 2.76 times, the wavelength of the light source is 680 nm, and the distance between the two light sources is 0.15 mm. The distance between the light source 1 and the collimator lens 2 is 7.96 mm, the distance between the collimator lens 2 and the cylindrical lens 3 is the sum of 7.96 and 29.1, 37.06 mm, and the distance between the cylindrical lens 3 and the lens 5 is 29.1 and 81.37.
Is 110.47 mm, and the distance between the lens 5 and the light deflecting means 7 is
81.37 mm. As shown in FIG. 3, the light beam width in the sub-scanning direction is determined by the width D in the sub-scanning direction of the slit 4 arranged on the light deflecting means 7 by 29.1 mm from the cylindrical lens 3.

On the other hand, the light beam in the main scanning direction travels as shown in FIG. The parallel light emitted from the collimator lens 2 becomes parallel light expanded or reduced by the cylindrical lens 3 and the lens 5, is deflected and scanned by the light deflecting unit 7, and passes through a scanning lens system including the lens 8 and the lens 9. The image is formed as a spot 10A and a spot 10B on the medium 10 to be scanned. The light emitted from the first light beam 1A and the second light beam 1B intersect at a position 7.96 mm behind the collimator lens 2 and near the light deflecting means 7.

At the position of the slit 4, as shown in FIG. 5, each light beam is 0.55 mm (0.15 × 29.1 / 7.9) in the main scanning direction.
Required from 6. ) A linear image with a width W is formed at a distance.

The beam width at this position in the sub-scanning direction at 1 / e ＾ 2 intensity can be obtained from equation (2), where f0 is the focal length of the collimator lens, and θ is the half-width of the light source in the sub-scanning direction. 1.7 is the ratio of the divergence of the beam having a half width and 1 / e ＾ 2 intensity width. W = 1.7 × 2 × f0 × sin (θ / 2) (2) Assuming that the diverging half-value angle of the light source in the sub-scanning direction is, for example, 13.8 degrees and the focal length of the collimator lens is 7.96 mm, equation (2)
Therefore, the beam width W in the sub-scanning direction is 3.25 mm. At this time, from equation (1), the spot diameter is 60 μm. If the target spot diameter is 60 μm, the value is as desired. If the divergence angles of the two beams are the same, a beam of uniform size can be scanned.

However, if the light spread angles of the two light sources vary, the spot diameter changes accordingly. For example, when the divergence angle of the first light source is 13.8 degrees and the divergence angle of the second light source is 16.6 degrees, from Equations (1) and (2), the spot diameter is The beam is 60 μm, and the beam from the second light source is 50 μm. In this case, the scanning line width varies, causing a problem in print quality.

In the present invention, a slit as shown in FIG. 6 is used, and is mounted on the opposite side of the light source from the cylindrical lens at a position separated by a focal length of the cylindrical lens and the slit width is set to be equal to that of the two spot diameters. Can be adjusted to be Specifically, 3.25 at the first beam
mm and about 3.25 mm at the second beam.

In addition, spot diameters may vary due to variations in the wavelengths of the two light sources. Target spot diameter
When the spread angle of the light source is sufficiently large and the change in the imaging position due to the wavelength difference due to the correction of the optical system is sufficiently small,
The wavelength of light from the first light source is 650 nm, and the wavelength of light from the second light source is 700 nm. At this time, when the slit width in the sub-scanning direction is 3.25 mm, from equation (1), the spot diameter of the beam from the first light source is 57 μm, and the spot diameter of the beam from the second light source is 62 μm. In the present invention, the slits shown in FIG.
μm. Specifically, the slit width of the beam from the first light source is 3.10 mm, the slit width of the beam from the second light source is approximately 3.34 mm
What should I do?

In addition, the spot diameter on the medium to be scanned may vary due to the variation of the imaging position of the spot from the two light sources due to the astigmatic difference. Also in this case, two spot diameters can be made uniform by adjusting the slit width for each beam.

In addition to the slits described so far,
If the slits are configured as shown in FIG. 8, the beam width can be adjusted independently of each other. If the number of slits is set to a number corresponding to the number of beams, three or four or more beams can be used.

Further, the slit opening may be triangular as shown in FIG. 9 or trapezoidal as shown in FIG.

In addition to the slits shown in FIGS. 8 and 6, by moving the slit in the scanning direction, the slit width can be adjusted, which is convenient for fine adjustment of the spot diameter.

In the above-described configuration in which a slit is formed, it is necessary to adjust the light output of the light source so that the light output of each spot becomes equal after adjusting the spot diameter on the medium to be scanned.

[0021]

As described above, according to the present invention, even when the spot diameters in the sub-scanning direction are not uniform due to differences in beam width due to variations in the spread angle of the light source, the slits are shaped. Sub-scanning on the medium to be scanned is achieved by arranging the cylindrical lens closer to the light deflecting means from the cylindrical lens closer to the light source in the lens system by the focal length of the cylindrical lens and making the widths of the plurality of light beams appropriate. The size of the directional spot diameter can be made uniform.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a view showing the vicinity of a cylindrical lens according to the embodiment of the present invention shown in FIG. 1;

FIG. 3 is a diagram of the embodiment of the present invention viewed from the side with respect to a main scanning plane.

FIG. 4 is a diagram of the embodiment of the present invention as viewed from above with respect to a main scanning plane.

FIG. 5 is a diagram showing light rays near a slit arrangement.

FIG. 6 is an explanatory view showing an embodiment of a slit.

FIG. 7 is an explanatory view showing an embodiment of a slit.

FIG. 8 is an explanatory view showing an embodiment of a slit.

FIG. 9 is an explanatory view showing an embodiment of a slit.

FIG. 10 is an explanatory view showing an embodiment of a slit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 2 beam light source, 2 ... collimator lens, 3 ... cylindrical lens, 4 ... slit, 5, 8, 9 ... lens, 6
... Motor, 7 ... Light deflecting means, 10 ... Medium to be scanned, 1A,
3A: first light beam, 1B, 3B: second light beam, 10A ...
1st light spot, 10B ... second light spot, 11 ... slit base, 12 ... screw, 13 ... edge plate.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 7/00 H04N 1/036 Z H04N 1/036 B41J 3/00 D 1/113 H04N 1/04 104A F Term (reference) 2C362 AA11 AA17 AA26 AA29 AA34 AA35 AA40 AA43 AA47 AA48 BA58 BA67 BA84 BA90 DA03 2H045 AA01 BA22 BA32 CB01 CB24 DA02 5C051 AA02 CA07 DA02 DB02 DB22 DB24 DB30 DB35 DC02 DA07 DA02 DA07 DA02 DA07 HA13 HB10 XA05

Claims (5)

[Claims] 1. A coupling lens system for collimating light beams from a plurality of light sources, a shaping lens system for shaping the light beams, a light deflecting means for deflecting and scanning the subsequent light beams, and a medium to be scanned for the deflected light beams. In a light scanning apparatus comprising a scanning lens system for forming an image, a plurality of light sources are arranged in parallel or at a small angle to the main scanning direction, and the shaping lens system has power in the main scanning direction at a position closest to the light source. An optical scanning device including a positive cylindrical lens, and a slit that restricts a light flux width in the sub-scanning direction at a position away from the cylindrical lens in a direction opposite to a light source by approximately a focal length of the cylindrical lens. . 2. The optical scanning device according to claim 1, wherein said slit has a plurality of independently adjustable edge portions. 3. When the interval of the edge portion in the main scanning direction is L, the interval of the light source in the main scanning direction is a, the focal length of the coupling lens system is f1, and the focal length of the cylindrical lens is f2, 3. The optical scanning device according to claim 2, wherein a relationship of L = a * f2 / f1 is satisfied. 4. The optical scanning device according to claim 1, wherein said slit has a width in the main scanning direction for passing a plurality of light beams at the same time, and a pair of edge portions is not parallel. 5. An optical scanning device according to claim 4, wherein said slit is movable in the main scanning direction and can be fixed.